Transmission assembly for transmitting torque across an angular connection between a torsional drive component and a torsionally driven component

ABSTRACT

A transmission assembly includes a cavity in a female U-joint having a groove that extends radially outward from an inner diameter thereof and bounded by three planar drive surfaces. A male U-joint member includes a drive end includes a longitudinal rectangular extension protruding radially outward from a periphery and positioned within the groove of the cavity. The drive end includes a longitudinal rectangular insert has a portion forming the extension positioned within the groove and retained within the drive end. The extension includes (1) opposing longitudinal sides, each forming a side crest disposed between a pair of angular side surfaces that extend axially from the side crest inward toward a center of the extension, and (2) a top side forming a top crest disposed between a pair of angular top surfaces that extend axially from the top crest downward toward the center of the extension.

REFERENCE TO PENDING PRIOR PATENT APPLICATION

This application is a divisional of U.S. patent application Ser. No.16/384,389, filed Apr. 15, 2019, which is now U.S. Pat. No. 11,137,033,by Gregory Clarence Goff, Patrick Daniel Gallagher, Daniel RobertGallagher, and Krista D. Anderson, for “DOWN-HOLE MOTOR UNIVERSAL JOINTASSEMBLY,” which is a continuation-in-part of U.S. patent applicationSer. No. 16/166,819, filed Oct. 22, 2018, which is now U.S. Pat. No.11,092,199, by Gregory Clarence Goff, Patrick Daniel Gallagher, andDaniel Robert Gallagher, for “DOWN-HOLE MOTOR UNIVERSAL JOINT ASSEMBLY,”which patent application is incorporated by reference herein.

BACKGROUND

Down-hole mud motors are used to apply torque to a drill bit in oil andgas wells and other drilling applications. The mud motor is placed at adistal end of the drill string, with a drill bit connected to a distalend of an output shaft. Drilling fluid or “mud” pumped through the drillstring flows through the mud motor, and the motor uses the force of thefluid to produce a mechanical output to rotate the output shaft and thedrill bit.

Although there are different types of mud motors, the most commonly usedtype today is a positive-displacement motor which uses an elongated,helically-shaped rotor within a corresponding helically-shaped stator.The flow of drilling fluid or mud between the stator and the rotorcauses the rotor to orbit within the stator eccentrically about alongitudinal axis of the stator. The rotor itself rotates about its ownlongitudinal axis and also orbits eccentrically around the centrallongitudinal axis of the stator. This eccentric orbit and rotation ofthe rotor must be transferred by a suitable transmission assembly toproduce a concentric rotation for the output shaft.

Universal joint assemblies, commonly referred to as U-joints, arerequired in order to transfer the eccentric orbit and rotation of therotor to the concentric rotation of the output shaft to drive the drillbit. To currently accomplish this, an output end of the rotor isconnected to a first U-joint, and a shaft connects the first U-joint toa second U-joint. The second U-joint is, in turn, connected to aconcentrically rotating output shaft.

In addition to transferring the eccentric rotation of the rotor to aconcentrically rotating shaft, down-hole mud motors may require otherU-joints. For example, a mud motor may be designed with a bent housingfor use in directional drilling. Mud motors may also include a mechanismby which the housing may be bent at a suitable angle for a particulardirectional drilling effect. In either case, a U-joint may be requiredto traverse the bend in the housing.

Regardless of how a U-joint is used in a down-hole mud motor, suchU-joints are subjected to very high torques and operate in a veryhostile environment.

U.S. Pat. No. 5,267,905 to Wenzel et al. discloses one example of aprior art U-joint assembly for a down-hole mud motor. The Wenzel deviceand other existing U-joints include articulating joint members with aseries of peripherally spaced balls on one joint member transmittingtorque from one U-joint member to the other. Still other existingU-joints include articulating joint members with a series ofperipherally spaced barrel rollers transmitting torque from one U-jointmember to the other. The torque transmitting balls and barrel rollersprovide a positive coupling between the two joint members. However, theballs and/or barrel rollers are each held within a corresponding dimpleformed in one of the joint members and, therefore, must rotate withrespect to the dimple surface as the joint articulates. This rubbingaction between the torque transmitting ball or barrel roller and thedimple in which it is held can cause excessive wear to the ball orbarrel roller and the dimple, eventually damaging the joint.

Specifically, the ball- and barrel-shaped driving elements act as awedge as they attempt to roll out of the concave receptacles they residein. This, in turn, generates an extreme radial force that causesdistortion to the concave receptacles formed in, for example, the drivehead of the male U-joint member and to the corresponding axial groovesof the receptacle of the female U-joint member that receives the maleU-joint member. Such distortion creates clearance between the ball orbarrel shaped drive elements and the axial grooves of the femalereceptacle and the concave receptacles of the drive head. As thisclearance increases, vibration and torque backlash generated by thedrill bit eventually increase the clearance to the point of multiplecomponent failures, which, in turn, causes the failure of the mud motoritself due to the transmission failure.

Another problem with prior art mud-motor U-joints involves the sealstructure that protects the bearing surfaces within the joint. Seals forU-joints used in mud motor applications must allow smooth articulationas the joint rotates, while protecting the internal bearing surfaces ofthe joint from extreme pressure, pressure variations, and high velocitydrilling fluid. Should these seals fail, the joint is exposed to thehostile environment of the drilling fluid, and rapid wear and failuremay occur.

Yet another problem with current drive shaft assemblies is the requisiteuse of two U-joint assemblies to accommodate an articulating joint, oneon each end of a common shaft, which increases the chance of componentfailure.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key aspects oressential aspects of the claimed subject matter. Moreover, this Summaryis not intended for use as an aid in determining the scope of theclaimed subject matter.

One embodiment provides a universal joint (U-joint) assembly fortransmitting torque from a drive component to a driven component acrossan articulating joint. The U-joint assembly may include a female U-jointmember coupled with the driven component, the female U-joint memberdefining a longitudinal axis and including a receptacle end, thereceptacle end comprising: (1) a cavity extending into the receptacleend and terminating in a circular receptacle; and (2) four flat surfacesextending longitudinally from the cavity at 90-degree intervals about aninner diameter of the cavity. The U-joint assembly may also include amale U-joint member coupled with the drive component and having a driveend, the drive end comprising four multi-angled surfaces extendinglongitudinally from the drive end at 90-degree intervals about aperiphery of the drive end. When the drive end of the male U-jointmember is received coaxially within the cavity of the female U-jointmember, each of the multi-angled surfaces of the drive end of the maleU-joint member opposes a corresponding one of the four flat surfaces ofthe female U-joint member.

Another embodiment provides a transmission assembly for transmittingtorque across an angular connection between a torsional drive componentand a torsionally driven component. The transmission assembly mayinclude (1) a flexible shaft operably coupled with the torsional drivecomponent; and (2) a single universal joint (U-joint) assembly operablycoupled between the flexible shaft and the driven component, the singleU-joint assembly comprising a female U-joint member defining alongitudinal axis, a central ball seat seated within the female U-jointmember, and a male U-joint member axially mounted about the central ballseat and within the female U-joint member.

Yet another embodiment provides a method of transmitting a torque from adrive component to a driven component across an angled joint. The methodmay include the step of positioning a universal joint (U-joint) assemblyat the angled joint, the U-joint assembly comprising: (1) a femaleU-joint member coupled with the driven component, the female U-jointmember defining a longitudinal axis and including a receptacle end, thereceptacle end comprising a cavity extending into the receptacle end,the cavity terminating in a circular receptacle and including four flatsurfaces extending longitudinally from the cavity at 90-degree intervalsabout an inner diameter of the cavity; and (2) a male U-joint membercoupled with the drive component and having a drive end comprising fourmulti-angled surfaces extending longitudinally from the drive end at90-degree intervals about a periphery of the drive end, the drive endreceived coaxially within the cavity of the female U-joint member suchthat each of the multi-angled surfaces of the drive end of the maleU-joint member opposes a corresponding one of the four flat surfaces ofthe cavity of the female U-joint member. The method may further includethe steps of articulating the male U-joint member about the longitudinalaxis such that the male U-joint member is disposed at an angle relativeto the longitudinal axis that is equal to an angle of the angled joint,and actuating the drive component such that the torque is transmittedfrom the male U-joint member to the female U-joint member through acontact area between select ones of the four multi-angled surfaces thatare positioned parallel to the angle of the male U-joint member andopposing ones of the flat surfaces of the female U-joint member.

An additional embodiment provides a U-joint assembly for transmittingtorque from a drive component to a driven component across anarticulating joint. The U-joint assembly may include a female U-jointmember coupled with the driven component, the female U-joint memberdefining a longitudinal axis and including a receptacle end, thereceptacle end comprising: (1) a cavity extending into the receptacleend and terminating in a circular receptacle; and (2) a plurality oflongitudinal rectangular grooves extending radially outward at equalintervals from an inner diameter of the cavity, each of the longitudinalrectangular grooves bounded by three drive surfaces. The assembly mayalso include a male U-joint member coupled with the drive component andhaving a drive end, the drive end comprising a plurality of longitudinalrectangular extensions extending radially outward from a periphery ofthe drive end. When the drive end of the male U-joint member is receivedcoaxially within the cavity of the female U-joint member, each of thelongitudinal rectangular extensions of the drive end is received withina corresponding one of the longitudinal rectangular grooves of thecavity of the female U-joint member.

Still another embodiment provides a transmission assembly fortransmitting torque across an angular connection between a torsionaldrive component and a torsionally driven component. The transmissionassembly may include (1) a flexible shaft operably coupled with thetorsional drive component; and (2) no more than one universal joint(U-joint) assembly operably coupled between the flexible shaft and thedriven component, where the U-joint assembly includes a female U-jointmember coupled with the torsionally driven component and defining alongitudinal axis, a central ball seat seated within the female U-jointmember, and a male U-joint member coupled with the flexible shaft andaxially mounted about the central ball seat and within the femaleU-joint member in a manner that transmits a torsional force applied bythe torsional drive component upon the male U-joint member to the femaleU-joint member in a perpendicular direction to the longitudinal axis.

Yet another embodiment provides a method of using a universal joint(U-joint) assembly to transmit a torque from a drive component to adriven component across an articulating joint. The method may includethe following steps: (1) coupling a female U-joint member with thedriven component, the female U-joint member defining a longitudinal axisand including a receptacle end comprising a cavity extending into thereceptacle end, the cavity having a plurality of rectangular channelsextending radially outward at equal intervals from an inner diameter ofthe cavity, each of the rectangular channels defined by three planardrive surfaces; (2) coupling a male U-joint member with the drivecomponent, the male U-joint member having a drive end comprising aplurality of rectangular extensions protruding radially outward at equalintervals from an outer periphery of the drive end, each of therectangular extensions defined by a top side and opposing longitudinalsides, the top side defined by two downward angular surfaces extendingaxially away from either side of a top apex and each of the longitudinalsides defined by two inward angular surfaces extending axially away fromeither side of a side apex; (3) positioning the drive end coaxiallywithin the cavity of the female U-joint member such that each ofrectangular extensions of the drive end is received within acorresponding one of the rectangular channels of the cavity; and (4)using the drive component, articulating the male U-joint member relativeto the longitudinal axis such that the male U-joint member articulatesrelative to the longitudinal axis, thereby causing a contact betweenselect ones of the downward and the inward angular surfaces of the maleU-joint member and opposing ones of drive surfaces of the female U-jointmember to transmit the torque from the male U-joint member to the femaleU-joint member in directions perpendicular to the downward and theinward angular surfaces.

Additional objects, advantages and novel features of the technology willbe set forth in part in the description which follows, and in part willbecome more apparent to those skilled in the art upon examination of thefollowing, or may be learned from practice of the technology.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments of the present invention,including the preferred embodiment, are described with reference to thefollowing figures, wherein like reference numerals refer to like partsthroughout the various views unless otherwise specified. Illustrativeembodiments of the invention are illustrated in the drawings, in which:

FIGS. 1A-1D illustrate respective side-exploded, perspective-exploded,side-plan, and cross-sectional views of one embodiment of a universaljoint (U-joint) assembly for transmitting torque across an articulatingjoint;

FIGS. 2A-2C illustrate respective perspective, side-plan, andcross-sectional views of one embodiment of a male U-joint member of theU-joint assembly of FIGS. 1A-1D;

FIGS. 3A-3D illustrate respective perspective, side-plan, andcross-sectional views of one embodiment of a female U-joint member ofthe U-joint assembly of FIGS. 1A-1D;

FIGS. 4A-4D illustrate respective perspective, top-plan, side-plan, andcross-sectional views of one embodiment of a central ball seat of theU-joint assembly of FIGS. 1A-1D;

FIGS. 5A-5C illustrate respective perspective-exploded, side-exploded,and front-exploded views of one embodiment of a retaining device of theU-joint assembly of FIGS. 1A-1D;

FIGS. 6A-6B illustrate respective side-plan and cross-sectional views ofone embodiment of a flexible shaft for operable connection to theU-joint assembly of FIGS. 1A-1D;

FIGS. 7A-7C illustrate respective exploded-perspective, side-plan, andcross-sectional views of one embodiment of a drive assemblyincorporating the U-joint assembly of FIGS. 1A-1D coupled with theflexible shaft of FIGS. 6A-6B;

FIG. 8 illustrates a perspective view of an alternative embodiment of adrive end of the male U-joint member of FIGS. 2A-2C;

FIG. 9 illustrates a perspective view of an alternative embodiment ofthe retaining device of FIGS. 5A-5C;

FIGS. 10A-10B illustrate respective side-plan and cross-sectional viewsof one embodiment of an alternative drive assembly including two U-jointassemblies shown in FIGS. 1A-1D connected by a common cylindrical shaft;

FIG. 10C illustrates a perspective view of one embodiment of a drivesub-assembly including the drive assembly of FIGS. 10A-10B with thefemale U-joint members, central ball seats, and retaining devices of theU-joint assemblies removed to reveal the male U-joint members and thecommon cylindrical shaft of FIGS. 10A-10B;

FIGS. 11A-11B illustrate respective side-plan and cross-sectional viewsof another alternative embodiment of a drive assembly featuring thefemale U-joint member of FIGS. 3A-3D, the central ball seat of FIGS.4A-4D, the retaining device of FIGS. 5A-5C, and a flexible shaft thatincorporates an embodiment of a drive end of the male U-joint member ofFIGS. 2A-2C;

FIG. 12 illustrates a side-plan view of one embodiment of the driveassembly of FIGS. 11A-11B, as assembled to an upper male radial bearing,which is, in turn, assembled to an output shaft of a mud motor andplaced within a sectional view of a fixed bend housing;

FIG. 13 provides a flowchart depicting an exemplary method of using anembodiment of one of the drive assemblies of FIGS. 7A-7C, 10A-10C, and11A-11B to transmit torque across an articulating or angled joint;

FIG. 14 illustrates a perspective view of an alternative embodiment of adrive end of the male U-joint member of the U-joint assembly of FIGS.1A-1D;

FIGS. 15A-15D illustrate respective perspective, longitudinal side, end,and bottom views of one embodiment of a rectangular-shaped machinedinsert of the drive end of FIG. 14 ;

FIGS. 16A-16B illustrate respective side-plan and cross-sectional viewsof an alternative embodiment of a receptacle end the female U-jointmember of FIGS. 1A-1D; and

FIGS. 17A-17B illustrate respective end and cross-sectional views of anassembly including the male U-joint member drive end of FIG. 14coaxially received within the female U-joint member receptacle end ofFIGS. 16-16B.

DETAILED DESCRIPTION

Embodiments are described more fully below in sufficient detail toenable those skilled in the art to practice the system and method.However, embodiments may be implemented in many different forms andshould not be construed as being limited to the embodiments set forthherein. The following detailed description is, therefore, not to betaken in a limiting sense.

Various embodiments of the systems and methods described herein relateto universal joint assemblies, or U-joint assemblies, for transferringtorque in a variety of drilling environments involving a down-hole mudmotor including, for example, transferring torque between aneccentrically rotating rotor and a concentrically rotating output shaftof a mud motor to drive a drill bit or in traversing a bend in a housingof a mud motor. More specifically, this description discussesembodiments of a U-joint assembly that transmits torque across thearticulating joint assembly, or between U-joint members, by maintaininga near constant face-to-face contact between a male U-joint member and afemale U-joint member as the joint articulates.

Embodiments of the disclosed U-joint assembly and associated driveassemblies may be operated in any drilling environment with minimal wearor damage to the components due to a minimal number of componentsrequired to form the assemblies, the primary material used tomanufacture the assembly components, and the ability for the U-jointassembly and drive assemblies to be operated in either a sealed andlubricated environment or, should a loss of sealing and lubricationoccur, operated with only drilling fluid as a lubricating fluid.

Turning to the exemplary embodiments, FIGS. 1A-1D illustrate respectiveperspective-exploded, side-exploded, side-plan, and cross-sectionalviews of one embodiment of a U-joint assembly 100 for transmittingtorque across an angled or articulating joint. In this embodiment, theU-joint assembly 100 may include a female U-joint member 104 defining alongitudinal axis L, as well as a male U-joint member 102, a centralball seat 106, and a retaining device 108, all coaxially mounted alongthe longitudinal axis, L.

FIGS. 2A-2C illustrate respective perspective, side-plan, andcross-sectional views of one embodiment of the male U-joint member 102.In this embodiment, the male U-joint member 102 may include amale-threaded end 110 separated from an opposing drive end 112 by asmaller diameter shaft 114 extending therebetween. The male-threaded end110 may form a male threaded connection 116 configured to be threadablyengaged directly or indirectly with an appropriate drive component suchas, for example, a rotor of a mud motor or a drive shaft coupled withthe rotor of the mud motor, as discussed below.

The drive end 112 may include four multi-angled faces 118, each situatedlongitudinally at a 90-degree interval about an outer circumference orperiphery of the drive end 112. Each of the multi-angled faces mayfeature a crown 126 located at an apex of a first angled surface 128 anda second angled surface 130 where each of the first and the secondangled surfaces 128, 130 angle away from the crown 126. Four convexradiused surfaces 120 may correspond to the four multi-angled faces 118,each traversing between a crest 122 of each one of the multi-angledfaces 118 to a root 124 of the adjacent multi-angled face 118. As shownin FIG. 2C, the drive end 112 may also include a conical end cavity 132that extends from a circular opening 134 within the drive end 112 to aconcave, semi-spherical bearing surface 136 at its termination.

FIGS. 3A-3D illustrate respective perspective, side-plan, longitudinalcross-sectional, and end cross-sectional views of one embodiment of thefemale U-Joint member 104. In this embodiment, the female U-joint member104 may include a male threaded end 138 and an opposing receptacle end140. The male threaded end 138 may form a male threaded connectionconfigured to engage directly or indirectly with an appropriate drivencomponent, such as, for example, a radial bearing or an output shaft ofa mud motor, as discussed further below.

The receptacle end 140 may include a female threaded connection 142 anda cavity 144 extending away from the female threaded connection 142. Inthis embodiment, the cavity 144 may include four flat surfaces 146extending longitudinally from the cavity 144 at 90-degree intervalsabout an inner diameter 145 of the cavity 144. Four concave radiusedsurfaces 143 may arc between each of the flat surfaces 146 and may alignwith or oppose the radiused surfaces 120 of the male U-joint member 102when the drive end 112 of the male U-joint member 102 is insertedcoaxially into the receptacle end 140 of the female U-joint member 104.The cavity 144 may terminate in a circular receptacle 148 located at thebottom of the cavity 144. A threaded lubrication channel 147 may extendlongitudinally from an end of the male threaded end 138 to the circularreceptacle 148.

FIGS. 4A-4D illustrate perspective, top-plan, side-plan, andcross-sectional views of one embodiment of the central ball seat 106,respectively. In this embodiment, the central ball seat 106 may includea flat circular base 150 having a centrally located shaft 152 thatextends proximally-to-distally therefrom. In an assembled configuration,a distal end 154 of the shaft 152 may terminate in a convexsemi-spherical bearing surface 156 configured to impinge upon theconcave semi-spherical bearing surface 136 of the conical end cavity 132of the male U-joint member 102, discussed above. A grease passage 158may be formed axially through the shaft 152 and the base 150 forlubrication purposes.

FIGS. 5A-5C illustrate respective perspective-exploded, side-exploded,and front-exploded views of one embodiment of the retaining device 108.In this embodiment, the retaining device 108 may include first andsecond semi-circular segments 160, 162 configured to clamp about theshaft 114 of the male U-joint member. Specifically, the first and thesecond semi-circular segments 160, 162 may be held in alignment aboutthe shaft 114 by two alignment sleeves 164 disposed within correspondingcounterbores 165 located 180 degrees apart from one another within thesecond semi-circular segment 162 and two appropriate fasteners 166(e.g., socket head fasteners). The fasteners 166 may secure the firstand the second semi-circular segments 160, 162 by extending through apair of alignment apertures 168 formed within the first semi-circularsegment 160, through the alignment sleeves 164 disposed within thecounterbores 165, and into a corresponding pair of threaded apertures170 formed in the second semi-circular segment 162, as shown in FIGS.5A-5B. In one embodiment, the assembled retaining device 108, formedfrom the assembled first and second semi-circular segments 160, 162, mayalso include a circumferential threading 172 about its circumference.The circumferential threading 172 may be threadably coupled with thefemale threaded connection 142 of the female U-joint member 104.

Returning to FIGS. 1C-1D illustrating the assembled configuration of theU-joint assembly 100, the retaining device 108 may be secured about thesmaller diameter shaft 114 of the male U-joint member 102 using thefasteners 166. In this regard, the retaining device 108 may be sized toprovide an articulation offset, O, between the shaft 114 and theretaining device 108 when the retaining device 108 is secured about theshaft 114. This articulation offset, O, provides sufficient space forradial movement of the shaft 114 within the retaining device 108 whenthe drive end 112 of the male U-joint member articulates within thecavity 144 of the female U-joint member 104.

The circular flat base 150 of the central ball seat 106 may be receivedwithin the circular receptacle 148 located at the bottom of thereceptacle cavity 144 of the female U-joint member 104. In turn, thedrive end 112 of the male U-joint member 102 may be inserted into thereceptacle cavity 144 of the receptacle end 140 of the female U-jointmember 104, thereby causing the convex semi-spherical bearing surface156 of the shaft 152 of the central ball seat 106 to be received by theconcave semi-spherical bearing surface 136 of the conical end cavity 132of the male U-joint member 102, such that the male and the femaleU-joint members 102, 104 may rotate and/or articulate about thelongitudinal axis, L, with the bearing surfaces 136, 156 impinging uponeach other. The circumferential threading 172 of the retaining device108 may be threaded into the female threaded connection 142 of thefemale U-joint member 104 to secure the female U-joint member 104 aboutthe central ball seat 106 and the drive end 112 of the male U-jointmember 102.

In one embodiment, a single U-joint assembly 100, as shown and discussedin relations to FIGS. 1-5 above, may be used in connection with a flexshaft 180, shown in FIGS. 6A-6B. Embodiments of the flex shaft 180 mayfeature opposing first and second ends 182, 184 separated by a flexibleshaft 185 disposed therebetween. The first end 182 of the flex shaft 180may form a female threaded connection 186, and the second end 184 of theflex shaft 180 may form a male threaded connection 188.

FIGS. 7A-7C illustrate respective perspective-exploded, side-plan, andcross-sectional views of a drive assembly 200 including a single U-jointassembly 100 assembled to and used in concert with an embodiment of theflex shaft 180. As assembled, the male threaded connection 116 of themale-threaded end 110 of the male U-joint 102 may be threaded into thefemale threaded connection 186 of the flex shaft 180. The U-jointassembly 100, and particularly the assembled drive assembly 200,transmits torque between the male U-joint member 102 and the femaleU-joint member 104 through an interfacing of the angled and radiusedsurfaces spaced about the periphery of the drive end 112 of the maleU-joint member 102 and about the inner diameter 145 of the cavity 144 ofthe receptacle end 140 of the female U-joint member 104.

Specifically, and as shown in FIG. 7C, as the drive end 112 of the maleU-joint member 102 articulates within the cavity 144 of the femaleU-joint member 104 relative to (e.g., in a direction orthogonal to) thelongitudinal axis, L, the first angled surface 128 of the drive end 112positioned parallel to an articulation angle of the flex shaft 180engages the corresponding opposing flat surface 146 (FIG. 3A) situatedlongitudinally about the inner diameter 145 (FIG. 3D) of the cavity 144of the female U-shaped member 102. At the same time, the second angledsurface 130 on the opposing side of the drive end 112, also positionedin parallel with the articulation angle of the flex shaft 180,simultaneously engages the corresponding opposing flat surface 146situated longitudinally about the inner diameter 145 of the cavity 144of the female U-shaped member 102. The crowns 126 positioned orthogonalto the engaged multi-angled surfaces 118—or the crowns 126 between thefirst and the second angled surfaces 128, 130 of the multi-angledsurfaces 118 offset 90 degrees from the engaged first and second angledsurfaces 128, 130—may engage the corresponding opposing flat surfaces146.

As the angle of the flex shaft 180 increases, an area of contact betweenthe respective angled surfaces 128, 130 of the male U-joint member 102and the flat surfaces 146 of the female U-joint member 104correspondingly increases, thereby transmitting torque from the maleU-joint member 102 to the female U-joint member 104. The angled surfaces128, 130 of the male U-joint member 102 and the flat surfaces 146 of thefemale U-joint member 104 may be configured such that the U-jointassembly 100 distributes the applied or driving torsional force over acombined surface area of at least 14 square inches, which spreads theforce over a substantial flat surface and dramatically reduces wear onthe joint and increases a life of the joint before failure.

The radiused surfaces 120 corresponding to each of the four multi-angledsurfaces 118 of the drive end 112 of the male U-joint member 102 (FIGS.2A-2B), each traversing between the crest 122 of each one of themulti-angled faces 118 to the root 124 of the adjacent multi-angled face118, provide substantial resistance to shearing from high-torque powersections. Moreover, the central ball seat 106 facilitates smootharticulation with minimal wear, while the convex semi-spherical bearingsurface 156 of the ball seat 106, which is seated within the concavesemi-spherical bearing surface 136 of the male U-joint member 102, actsas a thrust bearing between the male and the female U-joint members 102,104 to support significant axial loading.

In this embodiment of the drive assembly 200 incorporating the flexshaft 180, and due to the articulating nature of the U-joint assembly100 and the flexible nature of the flex shaft 180, a single U-jointassembly 100 accomplishes what has previously required two U-jointassemblies in existing designs, thereby saving money in both inventory,assembly time, and repair time required.

FIG. 8 provides a perspective view of an alternative embodiment of adrive end 112 a of the male U-joint member 102. In this embodiment, thedrive end 112 a includes features identical to the drive end 112 ofFIGS. 2A-2C, but contains a provision for the installation of a hardenedroller or cylindrical bearing 113 within a cylindrical pocket 115located on the crown 122 between each of the first and the second angledsurfaces 128, 130. The addition of the cylindrical bearing 113 serves toreduce frictional wear between the crowns 122 and the flat surfaces 146of the female U-joint member 104 during operation.

FIG. 14 illustrates a perspective view of another alternative embodimentof a drive end 112 b of the male U-joint member 102. In this embodiment,the drive end 112 b may include a plurality of rectangular-shapedextensions that protrude radially outward from the drive end 112 b. Inone embodiment, the extensions may take the form of a plurality ofmachined, rectangular-shaped inserts 402, each situated longitudinallyat equal intervals about and extending radially outward from an outercircumference or periphery of the drive end 112 b. Therectangular-shaped inserts 402 may each be received within and retainedby a corresponding receptacle 404 formed in an outer radial surface 406of the drive end 112 b. In other embodiments, the rectangular-shapedextensions may take any appropriate size, shape, type, and/orconfiguration. For example, in one embodiment, they may be incorporateddirectly into the drive end 112 b as manufactured protrusions.

FIGS. 15A-15D illustrate respective perspective, longitudinal side, end,and bottom views of one embodiment of the rectangular-shaped insert 402of the drive end 112 b of the male U-joint member 102. In thisembodiment, the rectangular-shaped insert 402 may have a generallyrectangular profile formed from two opposing longitudinal sides 408(i.e., identical left and right sides), two opposing ends 410, a topside 412, and a bottom side 414. Each of the opposing left and rightsides 408 may include a planar lower surface 415 and two upper angularsurfaces 416 extending axially from a side apex or crest 418 inwardtoward a center of the insert 402. Similarly, the top side 412 mayinclude two angular surfaces 420 extending axially from a top crest 422downward toward the center of the insert 402. In one embodiment, each ofthe side and top angular surfaces 416 and 420 may be angled away fromthe side and top crests 418 and 422, respectively, by an angle between1.5 and 5 degrees.

The bottom side 414 and the planar lower surfaces 415 of the opposingleft and right sides 408 of the insert 402 may be received and retainedwithin the corresponding receptacle 404, such that the angular surfaces416 and 420 of the opposing left and right sides 408 and the top side412, respectively, protrude outward from the receptacle 404, as shown inFIG. 14 . The inserts 402 may be retained within the receptacles 404 inany appropriate manner including, for example, an interference fit.

FIGS. 16A-16B illustrate respective side-plan and cross-sectional viewsof another embodiment of a receptacle end 140 b the female U-jointmember 104. In one embodiment, the receptacle end 140 b may define thelongitudinal axis, L, and be configured to coaxially receive the driveend 112 b of the male U-joint member 102, discussed above in relation toFIGS. 14 and 15A-15D.

In this embodiment, the receptacle end 140 b may include a similarconfiguration to the receptacle end 140, discussed above in relation toFIGS. 3A-3D, but may include a female threaded connection 142 b and acavity 144 b extending inward from the threaded connection 142 b. Thereceptacle cavity 144 b may include a plurality of rectangular channelsor grooves 430 situated radially at equal intervals about an innerdiameter 432 of the cavity 144 b in a pattern that mirrors the patternof the rectangular-shaped inserts 402 of the drive end 112 b of the maleU-joint member 102, discussed above, where each of the rectangularchannels or grooves 430 extends radially outward from an inner diameter432 of the cavity 144 b and is defined by three planar drive surfaces434.

In this embodiment, when the drive end 112 b of the male U-joint member102 is received coaxially within the receptacle cavity 144 b of thefemale U-joint member 104, as shown in FIGS. 17A-17B, the rectangularinserts 402 protruding from the drive end 112 b are received withinaligned ones of the rectangular channel/grooves 430 such that theangular surfaces 416 and 420 of the inserts 402 oppose correspondingones of the drives surfaces 434 of the rectangular grooves 430.

Under normal drilling operations, eccentric radial movement of the rotorwithin the stator and/or the angular bend of either a fixed bend or anadjustable angle housing causes the drive end 112 b of the male U-jointmember 102 to move at various articulation angles about the pivot of thecentral ball seat 106, relative to the longitudinal axis, L, defined bythe female U-joint member 140 b. This articulation relative to thelongitudinal axis, L, causes select ones of the angular surfaces 416,420 to come into contact with the corresponding opposing drive surfaces434 of the rectangular grooves 430 formed in the female receptacle end140 b. This contact between the respective side and top angular surfaces416 and 420 of the inserts 402 and the opposing drive surfaces 434 ofthe rectangular grooves 430 allows the resulting force of the torqueapplied to the drive head 112 b to be transmitted across a contact areabetween the angular surfaces 416, 420 and the opposing drive surfaces434 in a direction that is perpendicular to the angular surfaces 416 and420, thereby transmitting the torsional forces from the drive head 112 bof the male U-joint member to the receptacle end 140 b of the femaleU-joint member in a manner that eliminates the wedge effect that priorart balls and barrel rollers create in operation.

The drive end 112 b differs from the prior art ball and barrel rollersin that the assembled U-joint components may be operated in any drillingenvironment with minimal wear or damage to the components. In addition,the mated drive end 112 b of the male U-joint member 102 and thereceptacle end 140 b of the female U-joint member 104 may either beoperated in a sealed, lubricated environment or, should the loss ofsealing and lubrication occur, the assembly may function as designedwith only drilling fluid as a lubricating fluid. As discussed above,current ball-and-groove or barrel roller-and-groove arrangements haveminimal points of contact between the driving and driven components,which concentrates the applied torque to such a small area that thematerial yields immediately causing surface deformation, which leads torapid wear and failure.

FIG. 9 provides a perspective view of an alternative embodiment of aretaining device 108 a used in assembling the U-joint assembly 100. Inthis embodiment, the retaining device 108 a includes features identicalto the retaining device 108 detailed in FIGS. 5A-5C, but includes aretaining shoulder 109, which provides a leverage surface for theinstallation of a sealing boot or other gasket (not shown).

FIGS. 10A-10B illustrate side and cross-sectional views of oneembodiment of an alternative drive assembly 250. In this embodiment, thedrive assembly 250 may include two U-joint assemblies 100 connected by acommon cylindrical shaft 252 having integral provisions for a sealingboot installation. Specifically, and as shown in FIG. 10C showing adrive sub-assembly 254 comprising two of the male U-joint members 102coupled by the common cylindrical shaft 252 extending therebetween, theshaft 252 may having opposing first and second ends 256, 258. Each ofthe first and the second ends 256, 258 may include an O-ring groove 260,a retaining shoulder 262, and a radiused surface 264 configured toreduce the force of the drilling fluid bearing on the drive shaft boot.

FIGS. 11A-11B illustrate side and cross-sectional views of oneembodiment of an alternative drive assembly 300. In this embodiment, thedrive assembly 300 may include a flex shaft 180 a similar to the flexshaft 180 of FIGS. 6A-6B. Flex shaft 108 a may be identical to the flexshaft 180, except rather than a female connection, the first end 182 ofthe flex shaft 180 a may form the drive end 112 of the male U-jointmember 102. As assembled, the female U-joint member 104, the centralball seat 106, and the retaining device 108 may be assembled to thedrive end 112 of the flex shaft 180 b in the manner discussed above inrelation to FIGS. 1C-1D.

FIG. 12 illustrates a side view of the drive assembly 300 of FIGS.11A-11B, as assembled to an upper male radial bearing 310, which is, inturn, assembled to an output shaft 312 of a mud motor and placed withina sectional view of a fixed bend housing 314.

The components forming the U-joint assembly 100 and drive assemblies200, 250, and 300 may be formed of any appropriate material such as, forexample, 17-4 stainless steel, heat treated to a PH900 condition aftermachining, primarily for its corrosion resistance, abrasive resistance,and torsional strength. Some embodiments may be formed of 4145HT, 4330 VMOD, and/or 4130HT steels given their abilities to harden the drivesurfaces of the male and the female U-joint members. Both the male andthe female U-joint members 102, 104 are repairable via welding and theresurfacing of worn areas through either machining or hand grinding.

Embodiments of the male U-joint member 102, the flexible shaft 180, 180b, and the common cylindrical shaft 252 may be either machined frombillet or closed die forged to near net, with machining used to completethe features such as the cavity 144 terminating in the concavesemi-spherical bearing surface 136 and the angled surfaces 128, 130 ofthe male U-joint member 102. As new, higher torque power sections becomeavailable, the closed die forging process may become the preferredmethod of manufacture for these components.

Embodiments of the U-joint assembly 100 and the drive assemblies 200,250, 300 may be implemented in any high torque application in which thedriving and driven components require an angular connection. Asdiscussed above, exemplary operational environments include transferringtorque in a variety of drilling environments involving a down-hole mudmotor such as transferring torque between an eccentrically rotatingrotor and a concentrically rotating output shaft of a mud motor to drivea drill bit or in traversing a bend in a housing of a mud motor.

Embodiments the disclosed U-joint assembly and drive assemblies differfrom existing solutions in that the assembled components may be operatedin any drilling environment with minimal wear or damage to thecomponents due to the elegant design requiring minimal interfacingcomponents, the manufacturing materials, and the ability to operatewithin or in absence of a sealed, lubricated environment. ExistingU-joints and/or drive shafts utilizing ball and groove arrangementsfeature minimal points of contact between the driving and drivencomponents. This configuration concentrates the applied torque on asmall area and causes the material to yield immediately, resulting insurface deformation and leading to rapid wear and failure. The uniqueconfiguration of the disclosed U-joint assembly distributes the appliedtorsional forces through a combined surface area of 14 square inches,which spreads the force over substantial flat surfaces that minimizecomponent wear and drastically increase component life.

FIG. 13 provides a flowchart depicting an exemplary method (350) ofusing embodiments of the U-joint assembly 100, incorporating anembodiment of the male and the female U-joint members disclosed herein,and drive assemblies 200, 250, 300 to transmit torque across anarticulating or angled joint. In this embodiment, the method (350) maybegin with operably coupling the U-joint 100 between a drive componentsuch as a mud motor rotor and a driven component such as a mud motoroutput shaft (352). In one embodiment, the male U-joint member 102 maybe coupled with or incorporated into the flexible rod 180, 180 b. Inthis regard, the female U-joint member 104 may be operably coupled withthe driven component, or the mud motor output shaft 312, as shown inFIG. 12 , and the male U-joint member 102 may be operably coupled withthe drive component, or the mud motor rotor, via the flexible shaft 180,180 b.

The U-joint assembly 100 may be positioned at an angled or articulatingjoint such as, for example, a bend in the mud motor housing 314 (354),and the male U-joint member may be articulated relative to or in adirection orthogonal to the longitudinal axis, L, defined by the femaleU-joint member 104 until the male U-joint member 102 is disposed at anarticulation angle relative to the longitudinal axis, L (356). The drivecomponent may then be actuated such that a torque is transmitted acrossthe angled U-joint assembly, or from the male U-joint member 102 coupledwith the drive component to the female U-joint member 104 coupled withthe driven component (358). The transmission of torque occurs, in anexample employing the drive end 112 of the male U-joint member 102 andthe receptacle end 140 of the female U-joint member 104, through acontact between select ones of the first and the second angled surfaces128, 130, which combine to form the multi-angled surfaces 118, that arepositioned parallel to the articulation angle of the male U-joint memberrelative to the longitudinal axis, L, and opposing ones of the flatsurfaces 146 of the cavity 144 of the female U-joint member 102. Inanother example employing the drive end 112 b of the male U-joint member102 and the receptacle end 140 b of the female U-joint member 104, thetransmission of torque occurs through a contact between select ones ofthe side and the top angular surfaces 116, 120 and opposing ones of thedrive surfaces 434 of the rectangular grooves 430 formed in thereceptacle cavity 144 b of the female U-joint member.

Although the above embodiments have been described in language that isspecific to certain structures, elements, compositions, andmethodological steps, it is to be understood that the technology definedin the appended claims is not necessarily limited to the specificstructures, elements, compositions and/or steps described. Rather, thespecific aspects and steps are described as forms of implementing theclaimed technology. Since many embodiments of the technology can bepracticed without departing from the spirit and scope of the invention,the invention resides in the claims hereinafter appended.

What is claimed is:
 1. A transmission assembly for transmitting torqueacross an angular connection between a torsional drive component and atorsionally driven component, the transmission assembly comprising: aflexible shaft operably coupled with the torsional drive component; andno more than one universal joint (U-joint) assembly operably coupledbetween the flexible shaft and the driven component, the U-jointassembly comprising a female U-joint member coupled with the torsionallydriven component and defining a longitudinal axis, a central ball seatseated within the female U-joint member, and a male U-joint membercoupled with the flexible shaft and axially mounted about the centralball seat and within the female U-joint member in a manner thattransmits a torsional force applied by the torsional drive componentupon the male U-joint member to the female U-joint member in aperpendicular direction to the longitudinal axis: wherein the femaleU-joint member extends from a first end to an opposing second end alongthe longitudinal axis, the first end operably coupled with the drivencomponent, the second end forming a cavity terminating in a receptacleend and having a rectangular groove extending radially outward from aninner diameter of the cavity, the rectangular groove bounded by threeplanar drive surfaces; wherein the male U-joint member extends from afirst end to an opposing second end, the first end of the male U-jointmember coupled with the flexible shaft, the second end of the maleU-joint member comprising a drive end including a longitudinalrectangular extension protruding radially outward from an outerperiphery of the drive end, the drive end mounted coaxially within thecavity of the female U-joint member such that the longitudinalrectangular extension of the drive end is positioned within therectangular groove of the cavity; wherein the drive end of the maleU-joint member comprises a longitudinal rectangular insert having a topportion and a bottom portion, the top portion forming the longitudinalrectangular extension positioned within the rectangular groove of thecavity of the female U-joint member and the bottom portion received byand retained within a receptacle formed in an outer radial surface ofthe drive end; wherein the longitudinal rectangular extension comprises:opposing longitudinal sides, each forming a side crest disposed betweena pair of angular side surfaces that extend axially from the side crestinward toward a center of the longitudinal rectangular extension; and atop side forming a top crest disposed between a pair of angular topsurfaces that extend axially from the top crest downward toward thecenter of the longitudinal rectangular extension.
 2. The transmissionassembly of claim 1, wherein the pairs of the angular side surfaces andthe pair of the angular top surfaces each oppose an adjacent one of theplanar drive surfaces of the rectangular groove of the female U-jointmember such that when an eccentric radial movement of the torsionaldrive component causes an articulation of the drive end within thecavity relative to the longitudinal axis, the angular side surfaces andthe angular top surfaces contact the adjacent ones of the planar drivesurfaces to transmit the torsional force from the angular side surfacesand the angular top surfaces to the adjacent ones of the planar drivesurfaces.
 3. The transmission assembly of claim 1, wherein: the angularside surfaces are angled inward relative to the side crest between 1.5and 5 degrees; and the angular top surfaces are angled downward relativeto the top crest between 1.5 and 5 degrees.
 4. The transmission assemblyof claim 1 wherein the torsional drive component is a mud motor rotorand the torsionally driven component is a mud motor output shaft.